Definition : Circuit breaker is a mechanical device, capable of making,carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as short-circuit and over-current. Operating principle of Circuit Breaker : Most important function of the circuit breaker is the protection of the circuit at the abnormal operating conditions besides making, carrying and breaking the currents. Circuit breakers are equipped with some units to carry out protection function. Opening units of low voltage circuit breakers are defined as a release according to IEC 60947-2/EN 60947-2 standards and CE certificate. Releases : A release which permits a circuit breaker to open, without any intentional time delay. - Overcurrent releases - Undervoltage releases - Shunt releases All of the breakers are equipped with overcurrent releases. Undervoltage and shunt releases are not standard accessories, but they can be fixed on the breaker by the request of customer.